1. Field of the Invention
This invention relates to certain new phenoxybiphenyl and terphenyl compounds, to compositions containing phenoxy-biphenyl and terphenyl compounds in admixture with polyphenyl ethers, and to the application of these compounds and mixtures as functional fluids.
2. Description of the Prior Art
Many different types of materials are utilized as functional fluids and functional fluids are used in many different types of applications. Such fluids have been used as electronic coolants, diffusion pump fluids, synthetic lubricants, damping fluids, bases for greases, force transmission fluids (hydraulic fluids), heat transfer fluids, die casting release agents in metal extrusion processes and as filter mediums for air conditioning systems. Because of the wide variety of applications and the varied conditions under which functional fluids are utilized, the properties desired in a good functional fluid necessarily vary with the particular application requiring a functional fluid having a specific class of properties.
Of the foregoing, the use of functional fluids as heat transfer fluids has posed what is probably the most difficult areas of application. Thus, the requirements of a heat transfer fluid are as follows: The fluid should be liquid over a wide temperature range, and in general have a low vapor pressure so as to be utilized at atmospheric pressure. Such fluid should be operable as a heat transfer media over an extended period of time at given temperatures, and should exhibit a hign-degree of thermal and hydrolytic stability. Thus, a heat transfer fluid is often required to operate at temperatures in the order of 700.degree.F. or higher over extended periods of time. Such fluids, in addition, should be non-corrosive to metals with which they are in contact and in particular such fluids should be non-corrosive at the required operating temperature.
For vacuum pump diffusion oils, the viscosity characteristics of the fluid must be such that it may be used over a wide temperature range; that is, adequately high viscosity at high temperature, low viscosity at low temperature and a low rate of change of viscosity with temperature. Its volatility should be low at elevated temperatures of use and should be thermally and chemically stable in order to resist oxidation and decomposition so that it will remain uniform under conditions of use.